Rangaswamy Alana M M, Navals Pauline, Gates Eric W J, Shad Sammir, Watt Sarah K I, Keillor Jeffrey W
Department of Chemistry and Biomolecular Sciences, University of Ottawa Ottawa Ontario K1N 6N5 Canada
RSC Med Chem. 2022 Jan 26;13(4):413-428. doi: 10.1039/d1md00382h. eCollection 2022 Apr 20.
Tissue transglutaminase (TG2) is a multifunctional protein that plays biological roles based on its ability to catalyse protein cross-linking and to function as a non-canonical G-protein known as Ghα. The non-regulated activity of TG2 has been implicated in fibrosis, celiac disease and the survival of cancer stem cells, underpinning the therapeutic potential of cell permeable small molecule inhibitors of TG2. In the current study, we designed a small library of inhibitors to explore the importance of a terminal hydrophobic moiety, as well as the length of the tether to the irreversible acrylamide warhead. Subsequent kinetic evaluation using an activity assay provided values for the and parameters for each of these irreversible inhibitors. The resulting structure-activity relationship (SAR) clearly indicated the affinity conferred by dansyl and adamantyl moieties, as well as the efficiency provided by the shortest warhead tether. We also provide the first direct evidence of the capability of these inhibitors to suppress the GTP binding ability of TG2, at least partially. However, it is intriguing to note that the SAR trends observed herein are opposite to those predicted by molecular modelling - namely that longer tether groups should improve binding affinity by allowing for deeper insertion of the hydrophobic moiety into a hydrophobic pocket on the enzyme. This discrepancy leads us to question whether the existing crystallographic structures of TG2 are appropriate for docking non-peptidic inhibitors. In the absence of a more relevant crystallographic structure, the data from rigorous kinetic studies, such as those provided herein, are critically important for the development of future small molecule TG2 inhibitors.
组织转谷氨酰胺酶（TG2）是一种多功能蛋白质，它基于催化蛋白质交联的能力以及作为一种名为Ghα的非典型G蛋白发挥生物学作用。TG2的非调节活性与纤维化、乳糜泻和癌症干细胞的存活有关，这突出了TG2细胞可渗透小分子抑制剂的治疗潜力。在本研究中，我们设计了一个小型抑制剂文库，以探究末端疏水部分的重要性以及与不可逆丙烯酰胺弹头连接链的长度。随后使用活性测定法进行的动力学评估给出了这些不可逆抑制剂各自的 和 参数值。所得的构效关系（SAR）清楚地表明了丹磺酰基和金刚烷基部分赋予的亲和力，以及最短弹头连接链所提供的效率。我们还首次提供了这些抑制剂至少部分抑制TG2 GTP结合能力的直接证据。然而，有趣的是，本文观察到的SAR趋势与分子建模预测的相反——即更长的连接链基团应通过允许疏水部分更深地插入酶上的疏水口袋来提高结合亲和力。这种差异使我们质疑TG2现有的晶体结构是否适合对接非肽类抑制剂。在缺乏更相关晶体结构的情况下，来自严格动力学研究的数据，如本文提供的数据，对于未来小分子TG2抑制剂的开发至关重要。
